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author | Carlos Llamas <cmllamas@google.com> | 2023-12-01 17:21:32 +0000 |
---|---|---|
committer | Greg Kroah-Hartman <gregkh@linuxfoundation.org> | 2024-01-25 14:33:37 -0800 |
commit | 95b1d336b0642198b56836b89908d07b9a0c9608 (patch) | |
tree | 13cc8e1e8f0b8e617f1599232c7d7b22e5963e02 /kernel | |
parent | 5bb8270789c88c0e4ad78c0de2f274f2275c7f6c (diff) | |
download | linux-stable-95b1d336b0642198b56836b89908d07b9a0c9608.tar.gz linux-stable-95b1d336b0642198b56836b89908d07b9a0c9608.tar.bz2 linux-stable-95b1d336b0642198b56836b89908d07b9a0c9608.zip |
binder: fix race between mmput() and do_exit()
commit 9a9ab0d963621d9d12199df9817e66982582d5a5 upstream.
Task A calls binder_update_page_range() to allocate and insert pages on
a remote address space from Task B. For this, Task A pins the remote mm
via mmget_not_zero() first. This can race with Task B do_exit() and the
final mmput() refcount decrement will come from Task A.
Task A | Task B
------------------+------------------
mmget_not_zero() |
| do_exit()
| exit_mm()
| mmput()
mmput() |
exit_mmap() |
remove_vma() |
fput() |
In this case, the work of ____fput() from Task B is queued up in Task A
as TWA_RESUME. So in theory, Task A returns to userspace and the cleanup
work gets executed. However, Task A instead sleep, waiting for a reply
from Task B that never comes (it's dead).
This means the binder_deferred_release() is blocked until an unrelated
binder event forces Task A to go back to userspace. All the associated
death notifications will also be delayed until then.
In order to fix this use mmput_async() that will schedule the work in
the corresponding mm->async_put_work WQ instead of Task A.
Fixes: 457b9a6f09f0 ("Staging: android: add binder driver")
Reviewed-by: Alice Ryhl <aliceryhl@google.com>
Signed-off-by: Carlos Llamas <cmllamas@google.com>
Link: https://lore.kernel.org/r/20231201172212.1813387-4-cmllamas@google.com
[cmllamas: fix trivial conflict with missing d8ed45c5dcd4.]
Signed-off-by: Carlos Llamas <cmllamas@google.com>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
Diffstat (limited to 'kernel')
0 files changed, 0 insertions, 0 deletions